Paul....It makes me wonder if they couldn't just put a decent heat sink on those switchers and virtually eliminate the fan or at least make it very rare to ever turn on. I realize they want to keep them small and lightweight and I guess fans are cheap and light but I sure do hate the racket they make!
Steve N4LQ ----- Original Message ----- From: "Paul Christensen" <[email protected]> To: <[email protected]> Sent: Sunday, May 23, 2010 8:40 AM Subject: Re: [Elecraft] Samelex Power Supplies with a K3 >> Finally, I went back to my Aston 35m which has no fan and helps hold down >> the desk. Ahhh....No noise, No hash....Just nice clean DC. > > I've been dealing with the same issues as I transitioned from a 20 > year-old > Astron RS-35 to an HP bench supply and an Astron switcher. In each case, > both supplies use loud rotational fans. Recently, I've added fan speed > control with a PWM controller. Instead of limiting the fan's speed > through > current alone, a pulse-width-modulator controls speed by producing short > pulses of voltage. Speed is then controlled by the duty-cycle of the > circuit's pulse train. > > After trying several attempts to smoothly control rotational speed with > series resistors and voltage-dividers, I found several low-cost PWM kits > (~ > USD $20) available that accurately control speed down to slow levels > without > stalling. In the case of the SS-20, I created two threshold steps, one to > engage when the heatsink temperature rises above a pre-determined amount. > However, after adding the PWM controller and letting the idle speed rest > where no noise is heard, enough air flows to keep the higher speed from > kicking in, except when I key down into a load for more than a minute. > > Paul, W9AC > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
